From what I used Vista, its nice, but I made the stupid decision to put the 64bit version on and many drivers don't work now. I noticed some software including video and photo editing to run faster and uptime is better. Overall design is nicer. I'm still running the RC1 copy and just waiting till the real release comes out to upgrade. I wonder if beta testers will get a discount off the real copy.....
Little problem I had is with WMP DVD codec looks like it expired, and I gave up looking for a new one (I think mpeg2), though I use VLC mostly.

To add I really like Office 2007. Just the look and feel is nicer, with some new features.